1. Field of the Invention
The present invention relates to a resistance temperature sensor, and more particularly, it relates to a resistance temperature utilizing a property such that the resistance value of a resistor is varied with the temperature.
2. Description of the Background Art
FIG. 6 shows a conventional resistance temperature sensor 1, which is of interest to the present invention. This resistance temperature sensor 1 comprises an electrical insulating substrate 2 which is made of alumina, for example. A support part 3 is provided on one side portion of the insulating substrate 2 to be in contact with a member for supporting the resistance temperature sensor 1, while a circuit part 4 is provided on another side portion thereof. A zigzagging resistance circuit 5 is formed on the circuit part 4 of the insulating substrate 2. The resistance circuit 5, which is formed by a metal thin film of platinum, for example, is given a zigzagging form in the following manner:
A metal thin film is formed over the entire surface of the circuit part 4 of the insulating substrate 2 by sputtering, plating or baking with organic metal resinate, and provided with grooves 6 by irradiation with a laser, dry etching or wet etching. These grooves 6 divide the metal thin film, to define the zigzagging resistance circuit 5. A groove 7 which is formed by a similar method defines a boundary between terminal electrodes 8 and 9, which are connected with respective end portions of the resistance circuit 5. Further, grooves 10 are formed by a similar method along peripheral edges of the insulating substrate 2. Even if the metal thin film is partially separated from an end thereof, such separation is effectively stopped by a corresponding one of the grooves 10. Metal thin films defining the terminal electrodes 8 and 9 are formed simultaneously with the metal thin film forming the circuit part 4.
The terminal electrodes 8 and 9 are connected with lead wires (not shown) respectively.
In order to attain a high output in such a resistance temperature sensor 1, it is preferable to maximize the width of a region having a uniform temperature which is affected by heat generation of the resistance circuit 5. To this end, the metal thin films provided in the circuit part 4 are formed with constant thicknesses and the resistance circuit 5 is formed with a constant circuit width in general. Namely, resistance values in the respective portions are set at constant levels over the entire resistance circuit 5, so that the overall resistance circuit 5 uniformly generates heat.
When the resistance circuit 5 of the resistance temperature sensor 1 having the aforementioned structure is energized and subjected to measurement of temperature distribution, however, a result shown in the lower part of FIG. 6 is obtained. It is understood from FIG. 6 that relatively large heat escape based on heat conduction or the like exists at a side portion of the circuit part 4 which is close to the support part 3, i.e., a non-heating part, leading to a tendency to increase heat loss and thereby reduce uniformity of temperature distribution. Therefore, an output characteristic of the resistance temperature sensor 1 with respect to temperature change is reduced.